This invention refers to a molten salt central receiver arrangement and a method for operating the molten salt central receiver arrangement.
The basic design and function of a molten salt central receiver arrangement is described in A. K. Das et al. “Design features and control concepts of ALSTOM molten salt receiver”, International Conference on Concentrating Solar Power and Chemical Energy Systems, SolarPACES 2014, Energy Procedia 69 (2015), 350-359 available online at www.sciencedirect.com.
The molten salt central receiver arrangement contains a panel arrangement with multiple panels having tubes, through which molten salt may flow. Solar radiation is reflected by solar reflectors onto the panels. In so doing heat is transferred from the panel arrangement to the molten salt. The heated molten salt can be stored in a hot tank. The thermal energy of the molten salt can be used to generate steam and to drive a steam turbine to produce electric energy.
The problem with the molten salt is that it may freeze, if its temperature drops below a critical temperature value due to insufficient heating by means of the central receiver arrangement. To avoid freezing of the molten salt A. K. Das et al. propose to feed pressurized air into the panels in order to drain the molten salt from the panels and to fill the tubes of the panels with compressed air instead. The compressed air flows from an upper manifold and down through the panels of the panel arrangement to a lower manifold.
Draining of the panel arrangement is a critical operation. If draining is not achieved before the molten salt temperature drops to a critical value, one of the panels might be blocked due to freezing of the molten salt. Thus, the restart of the molten salt central receiver arrangement is time consuming, because the tubes of the panels have to be refilled with molten salt first, before the panels can be heated. Without a flow of molten salt through the panel tubes the heat of the panels cannot be transferred and the panels might be damaged. Consequently, the reliability and availability of the system is reduced when the panels are not properly drained.